The BBC engaged in a "major breach" of media regulations by not revealing that the presenter of a programme about Gaza was the offspring of a Hamas official, as ruled by UK media regulator Ofcom.
An probe by the broadcasting watchdog into Gaza: How to Survive a Warzone has found that the documentary was "substantially inaccurate".
The chief executive of the broadcaster had already issued an apology, stating there had been "a serious error in relation to factual correctness".
The regulator has ordered the BBC to transmit a prime-time declaration about its conclusions.
"Given this constitutes a serious breach of our regulations, we are ordering the corporation to broadcast a message of our findings against it on the BBC's second channel at nine o'clock in the evening, with a schedule to be finalised," it said.
'Potential to Damage Trust'
The authority's statement stated: "Our investigation determined that the documentary's omission to reveal that the presenter's male guardian occupied a post in the Hamas-administered authority was substantially inaccurate.
"It meant that the viewers did not have critical information which may have been highly relevant to their assessment of the narrator and the content he provided.
"Confidence is at the core of the bond between a broadcaster and its public, notably for a state-funded media outlet such as the public broadcaster.
"This error had the possibility to damage the significantly high levels of confidence that viewers would have invested in a BBC factual programme about the conflict in Gaza."
The film was pulled from the online platform in the month of February after the presenter's familial connections emerged, and in July an broadcaster's internal assessment determined it infringed the corporation's journalistic standards on accuracy.
A representative for the broadcaster stated: "The Ofcom ruling is in agreement with the conclusions of Peter Johnston's review, that there was a serious error in the film in relation to the broadcaster's journalistic policies on factual correctness, which corresponds to Rule 2.2 of Ofcom's Broadcasting Code.
"We issued an apology for this and we agree with Ofcom's decision in its entirety. We will adhere to the directive as soon as the timing and wording are finalised."
